Hopeless

So the guy that I lost my virginity to last September and I have been hooking up on and off since then. He doesn't like to use condoms and we dated for a short time because I really thought I cared about him (ha). Come to find out that this semester, he got a girlfriend and I had absolutely no idea and I asked about it and he said he didn't but he does and I just want to forget him. He's a terrible person, absolutely awful, and he treated me like garbage but I can't stop thinking about him and this dumb situation. How do I stop thinking about him? He's not worth my time.